Temperature indicator



Feb. 18,1941. EEBACQN Re. 21,716

TEMPERATURE INDICATOR Original Filed Feb. 2'7, 1935 Reissued Feb. 18, 1941 UNITED. STATES PATENT OFFICE TEM RATURE INDICATOR.

. Elbridge F. Bacon,

Flint, Mich, assignor to General- Motors Corporation, Detroit, Mich., a corporationof Delaware ori inal'no ai aelo, dated April No. 8,426, February 27, 1935.

12, 1938, Serial Application for reissue January 26, 1948, Serial No. 315,840

. 8 Claims.

This invention relates to temperature indica tors and has particular reference to the temperature indicators applied to the internal combustion engines used on automotive vehicles.

Internal combustion engines used on automotive vehicles are customarily suppliedwith a cooling system in which there iscirculated a supply of water to keep the cylinders from overheating. It is desirable toknow the'temperature of the 19] water in the cooling system for the reason that excessive temperatures of 200 indicate that the water is shortly to reach the' boiling point and that the supply of water in :the'system needs to be replenished. For this reason temperature in- 15 dicators are used'having a dial or signal at the dash board to indicate to the operator when the engine is being overheated or when the liquid in the system needs to be replenished.

In the present invention use is made of an 20 electric circuit having a signal or indicator at the dash board. In the circuit there is placed a,

tion of the electric circuitwhen the running conditions of the engine are normal or when the water is at a relatively low temperature such as 150 and below, but which will allow the current 35 to pass through the system'to operate a signal at the dash board when the temperatures are high, such as 180 and above. 'The material or element used is preferably boron.

n the drawing: t Figure 1 shows a portion of an automobile with the heat indicator installed.

Figure 2 is a section through the unit or plug secured to the engine block. Figure 3 is a sectionon the line 3-3 of 45 Figure x Figure 4 is a section through the dash board showing the signal at the dash.

Figure 5 is a' section through. the dash board v showing the switch to operate the signal of to Figure 4. v I I Referring to the drawing,- the numeral 2 indicates an automotive vehicle as a whole. The

' .vehicle has the usual hood 4', windshield 6, frame 0. The engine has-the usual head 8, and engine! I [4. Associated with "the engine 65 I2 and crank case is the starting motor I6 and driven, from the engine is the usual transmission, the housing of which is indicated at I8. The vehicle has the usual electrical battery 20 which is grounded to the. frame at 22. The usual instrument board is indicated at 24.

The resistor unit or plug of the invention is indicated as a whole at 26 and is shown in detail in Figures 2 and 3. The unit comprises the main body portion 28 having the hexagonal head 30 and the threads 32 to enable it to be applied to the corresponding threaded portion 34 in the head l2 of the engine block Ill. The body 28 is bored or hollow as indicated at 36 and has the bottom 38 which is in contact with the water of the cooling system, one of the passages of which is indicated at 48.

Interiorly of the bore 36 of the body 28 there is positioned the tube of insulating material 42 which extends the entire length of the bore. At the bottom of the bore there is positioned the circular metal plate or washer 44 having the annular flange '46. Over the plate there is positioned a quantity of boron 48 and over the boron there is positioned a second metal plate 50, a duplicate of the plate 44.

The head 30 of, the body 28 hasthe counter- 'bore 52 in which there is screwthreaded as at 54 the cup 56. The cup 56 has the squared portion 58 provided with an annular opening 60 at its center. The squared portion is shaped to form a recess 62 at the inner portion of the cup 56. In the recess 62 there is received the electric insulation 64 and on the outside of the squared portion there is applied the electric insulation 66 in the form of a square washer. A retaining member 68 in the form of a bolt is applied from the inside of the cup 56 so that the bolt head Ill abuts against the insulation 64 but is out of contact with the cup. Anenlarged portion I2 on the bolt closely fits into a corresponding opening in the insulating washer 64.-

A projection 14 extends from the center of the head toward the bore 36 of the body 28, and a spring 16 having a small end 18 adjacent the projection 14 extends from around the projection to the washer 58 where the large end 88 of the spring contacts the washer 58 to form an elec- J trical circuit from the-washer 44 through the boron 48, washer 50, spring 16, and head 18 to the exterior or threaded end 82 of the bolt 68.

' The usual metallic washer 84 is applied over the insulation 66 and a. nut 86 is threaded-on the threaded shank 82 rigidly and tightly to secure the parts together. A second nut 88 is threaded on the shank 82 and rigidly clamps between the two nuts the end or terminal 90 of a wire 92 of the electrical circuit.

Referring to Figure 4, it will be seen that the signal is in the form of a lamp 94, but if desired an audible signal such as a hell or buzzer could be used. The lamp is secured in the usual lamp socket 96 which is held in a suitable thimble 98 secured by means of a flange I00 to the dash board 24. The thimble is open at its inner end as indicated at I02 to allow for the passage of the wires 92 and I04. The ends of the wires are suitably secured to a piece of insulation I06, and a spring I 08 between the bottom of the thimble and the insulation I06 always urges the terminals IIO of the wires toward the terminals II2 of the lamp.

Referring to Figure 5, there is shown a conventional type of testing switch II4. This switch has the push button II6 mounted in thehousing II8 secured to the dash board 24 by means of the flange I20. A contact spring I22 always urges the push button II6 to the position shown in Figure 5 or away from the contact I24 and wire I26. The terminal I24 is held in the housing II8 by means of the insulating washer I28. A wire I29 leads from the switch II4 to ground.

Referring to Figure 1, it will be seen that the circuit from the battery 20 includes-the wire I80 which leads to the ignition switch I82, the key of which is indicated at I34. The circuit is therefore open or closed depending on whether the ignition is open or closed, respectively. From the ignition switch I32 the wire I04 leads to the signal 94 and from the signal the wire 92 leads to the unit 26, the body of which is grounded to the frame through the engine block I0. It is therefore apparent that the'slgnal 94 is not distinguishable at the dash unless the circuit indicated as a whole at I36 is closed through the unit 26 in the engine block. At lower temperatures of the water in the cooling system the resistance of the boron 48 is too great to allow suflicient current to pass through the circuit properly to illuminate the signal 94. However, when higher temperatures are reached such as temperatures 180 or higher, sufiicient current will pass through the boron to iluminate the light 94, and when temperatures as high as 212, or the boiling point of water, are reached, the resistance of the boron will he very low, such as approximately 2 ohms,'so that the light 94 is brightly illuminated.

The boron 48 is not a pure boron owing to ,its cost and the difliculty of obtaining it. The boron is of an impure type or may have mixed therewith a certain quantity of aluminum, copper, or graphite to increase its conductivity.

Pure boron oxidizes too readily and for this reason amorphous boron, which can be produced from a reduction process from boric acid, is used. A resistor formed by assembling powdered boron with gilsonite under considerable pressure forms a satisfactory product to use in theresistor unit 26. Resistor units having 150 ohms resistance at room temperature and a very low resistance at high temperatures can be formed in this manner.

Instead of the light 94 (or a bell) is diiTerential galvanometer orgauge such as shown in my Patents 1,791,786, February-10, 1931 and 1,942,529, January 9, 1934, may be used. With a gauge of this type, the pointer will indicate a plurality of temperatures, the position of the needle over the scale being determined by the or galvanometer coils to amount of current passing through the boron. The electrical resistance of the boron will depend on its temperature, and by suitably changing, calibrating and/or proportioning the gauge suit the range of resistance changes in the boron, the dial or scale of the gauge can be accurately divided properly to indicate the water temperature. The advantage of the gauge of my prior patents is that it gives a plurality of readings instead of one, as will be the case with the light or bell.

I claim:

4 1. In a. thermal resistor unit, a hollow resistor plug having a portion thereof in contact with the medium the thermal condition of which is to be determined, a quantity of boron in the plug, said boron being out of contact with the medium, means electrically to insulate said boron from the plug, and electrically conductive means at the ends of the quantity of boronto confine the boron and to complete an electric circuit therethrough.

2. In a thermal resistor unit, a hollow resistor plug having a portion thereof in contact with the medium the thermal condition of which is to be determined, a said boron being out of contact with the medium, means electrically to insulate said boron from the plug, electrically conductive means at the ends of the quantity of boron to confine the boron and to complete an electric circuitthere-- through, a. cup secured in one end of the plug, and an electrically conductive spring between the cup and said electrically conductive means.

3. In a thermal resistor unit for application to a temperature indicating system, an integral imperforate hollow plug closed at one end and open at the other, said plug adapted to be secured in position on the device having the medium the temperature of which is to be determined, the closed end of said plug being inside the device and the open end outside thereof, thermal responsive means in the bottom of the plug at the closed end responsive to changes in temperature to enable an electric current to pass therethrough, means to insulate said thermal means from the plug, a removable cap in the open end of the plug closing the open end, an electric contact secured to the cap, means to insulate the contact from the cap, and a compressed coil spring in the plug extending between the contact and the thermal responsive means in the plug end and in electrical contact with both, to enable an electric current to pass through the plug at higher temperatures.

4. In a thermal resistor unit for application to a temperature indicating system, an integral imperforate hollow plug closed at one end and open quantity of boron in the plug,

position on the device having the medium the temperature of which is to be determined, the closed end of said plug being inside the device and the'open end outside thereof, thermal responsive means in the bottom of the plug at the closed end responsive to changes in temperature to enable an electric current to pass therethrough, metallic electrically conducting plates at the ends of said thermal responsive means, means electrically to insulate one of said plates and said thermal responsive means from the plug, a removable cap in the open end of the plug closing the open end,

an electric contact secured to the cap, means to insulate the contact from the cap, and a compressed coil spring in the plug extending between the contact and the insulated plate in the plug end and in electrical contact with both, to enable an electric current to pass through the plug at higher temperatures.

5. In a thermal resistor unit, a hollow resistor plug having a portion thereof in contact with the medium the thermal condition of which is to be determined, a quantity of boron in the plug, said boron being out of contact with the medium, means electrically to insulate said boron from the plug, and electrically conductive means contacting with the boron to complete an electrical circuit therethrough.

6. In a thermal resistor unit, a hollow resistor plug having a portion thereof in contact with the medium the, thermal condition of which is to be determined, a quantity of boron in the plug, said boron being out of contact with the medium, means electrically to insulate said boron from the plug, electrical conducting members at both ends of the boron to hold the boron in place, and a spring between one of the members and one end of the plug to complete an electrical circuit.

'7. In a thermal resistor unit for application to a temperature indicating system, an integral imperforate hollow plug closed at one end and open at the other, said plug adapted to be secured in position on the device having the medium the temperature of which is to be determined, the closed end of said plug being inside the device and the open end outside thereof, thermal responsive means in the bottom of the plug at the closed end responsive to changes in temperature to change its resistivity to enable a greater or less amount of electric current to pass therethrough, means to insulate said thermal means from the plug, a cap at the open end of the plug closing the open end,

an electric contact secured to the cap, means to insulate the contact from the cap, and a compressed spring in the plug extending between the contact and the thermal responsive means in the plug end and in electrical contact with both, to enable an electric'current to pass through the plug at higher temperatures.

3. In a thermal resistor unit for application to a temperature indicating system, an integral imperforate hollow plug closed at one end and open at the other; said plug adapted to be secured in position on the device having the medium the temperature of which is to be determined, the closed end of said plug being inside the device and the open end outside thereof, thermal responsive means in the bottom of the plug at the closed end responsive to changes in temperature to change its resistivity to enable a greater or less amount of electric current to pass therethrough, metallic electrically conducting plates at the ends of said thermal responsive means, means electrically to insulate one of said plates and said thermal responsive means from the plug, a cap at the open end of the plug closing the open end, an electric contact secured to the cap, means to insulate the contact from the cap, and a compressed spring in l the plug extending between the contact and the insulated 'plate in the plug end and in electrical contact with both, to enable an electric current topass through the plug at higher temperatures.

ELBRIDGE F. BACON. 

